What Does PHP's Elvis Operator (?:) Do and How Does It Work?

The Elvis Operator (?:) in PHP

The ?: operator, also known as the "Elvis operator," evaluates the left operand if it's truthy and the right operand otherwise. In short, it's a shortcut for the following:

foo = bar ? bar : baz;

Consider the code:

$items = $items ?: $this->_handle->result('next', $this->_result, $this);

This code evaluates to $items if it's truthy (not empty or false), and evaluates to the $this->_handle->result('next', $this->_result, $this) expression otherwise.

Key Points:

• The ?: operator is similar to the ternary operator, but the expression to evaluate to if the predicate is true is omitted.
• foo ?: bar is equivalent to foo ? foo : bar.
• The ?: operator ensures that the left operand is evaluated only once.
• It can be used for "self-checking" of values, as seen in foo = foo ?: bar.
• The Elvis operator's name refers to its resemblance to Elvis Presley's iconic hairstyle.

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